Cementitious liquid screeds

[eandg]

Are they all much the same (so your local concrete man can sort it) or should we be looking for one of the proprietary brands? I see there are some which require a minimum thickness of only 25mm above pipework; is there any particular reason why you'd be looking for 50mm if you could get away with 41mm in that case?

[epsilonGreedy]

9 minutes ago, eandg said:

I see there are some which require a minimum thickness of only 25mm above pipework; is there any particular reason why you'd be looking for 50mm if you could get away with 41mm in that case?

 

 

Would you prefer a bit more thermal inertia in your slab?

 

Is your floor base level mm perfect? If not might an extra 10mm of screed cover up some errors? The thinnest flow screens are very runny. A set floor that leaves some UFH pipework exposed constitutes a major disaster.

 

10 minutes ago, eandg said:

if you could get away with 41mm in that case?

 

 

History is littered with the failures of over confident engineers.

 

My inclination when I arrive at this decision point will be to design for 60mm if a manufacturer claims 50mm will be ok though will need to ensure the extra depth does not generate too much heat and trigger an excessively fast cure.

 

[eandg]

Thanks - so 60mm to be on the safe side meaning at least 50mm on the high side is advisable?

[epsilonGreedy]

27 minutes ago, eandg said:

Thanks - so 60mm to be on the safe side meaning at least 50mm on the high side is advisable?

 

 

Yes but just my contrarian view. Those who sell branded anhydrate liquid screed sound convincing when promoting a thin screed but is this because they sell mainly to pro builders who look to shave a few ££s here and there.

 

When I get to the point of planning which insulation sheet thicknesses to buy to make up a finished floor 225mm high I will try and phone some technical departments to establish if there is a downside to going a bit deeper than standard.

 

I also need to get my line laser out to create a topographical map of my current block floor heights. I know of one 10mm dip mid floor but hope the periphery is within +/- 5mm.

[Adam2]

you may find that options will depend on local supplies, it was easier for me to get Longfloor - I was initialling looking at Cemfloor. The installer says Longfloor is what they mainly used as plant was only 20 mins away whereas Cemfloor was 1.5hr and they preferred less time in transit. Outcome is pretty good - couple of minor cracks - we poured about 16m3. Regarding cracks, they will use crack inducers but generally not as they usually result in some lipping at the inducer location apparently. They will come back and inspect in a few weeks and fill anything over 2mm. Depth wise - on my concrete slab bases we went with 50mm/55mm as they were pretty true. On the upper floors with precast planks I thought we should go with 65mm to be sure of pipe cover BUT in fact we used dried sand under the insulation (25mm) to ensure no voids which meant the insulation was very flat so could have gone with less. Longfloor & Cemfloor both being cementious screeds. On our pour day we had the bonus of the plant boss + the longfloor rep being there to do some videos - if this wasn't done right it never will be!

 

[eandg]

3 minutes ago, Adam2 said:

you may find that options will depend on local supplies, it was easier for me to get Longfloor - I was initialling looking at Cemfloor. The installer says Longfloor is what they mainly used as plant was only 20 mins away whereas Cemfloor was 1.5hr and they preferred less time in transit. Outcome is pretty good - couple of minor cracks - we poured about 16m3. Regarding cracks, they will use crack inducers but generally not as they usually result in some lipping at the inducer location apparently. They will come back and inspect in a few weeks and fill anything over 2mm. Depth wise - on my concrete slab bases we went with 50mm/55mm as they were pretty true. On the upper floors with precast planks I thought we should go with 65mm to be sure of pipe cover BUT in fact we used dried sand under the insulation (25mm) to ensure no voids which meant the insulation was very flat so could have gone with less. Longfloor & Cemfloor both being cementious screeds. On our pour day we had the bonus of the plant boss + the longfloor rep being there to do some videos - if this wasn't done right it never will be!

 

Thanks - looks very good. We've a Cemfloor supplier about half an hour away and I've asked for a quote.